This application claims priority under 35 USC 119(a) to Patent Application No. 2004-95914 filed in Japan on 29 Mar. 2004, the content of which is hereby incorporated herein by reference in its entirety.
The technology disclosed herein pertains to rotatable roller(s) rotating with an outer circumferential surface(s) thereof contacting and/or sliding against at least one electrostatic latent image carrier(s), and pertains to image forming apparatus(es) employing same, and pertains to image forming apparatus cartridge(s) employing same.
As is known, in electrophotographic image forming apparatuses, as a photosensitive drum (electrostatic latent image carrier) is made to rotate, a charging apparatus causes the surface of the photosensitive drum to become uniformly charged; a beam of light is scanned across the surface of the photosensitive drum, forming an electrostatic latent image on the photosensitive drum; developer is made to adhere to the electrostatic latent image on the photosensitive drum, forming a development image on the photosensitive drum; the development image is transferred from the photosensitive drum to recording paper; and heat and pressure are applied to the development image on the recording paper to fuse it thereon.
Here, the charging apparatus may be a device using corona discharge to generate/apply charge, a device using contact with roller(s) to generate/apply charge, and so forth. The former, i.e., corona-discharge-type charging apparatuses, are advantageous in that they apply charge to the photosensitive drum in noncontact fashion and in that they cause the surface of the photosensitive drum to become uniformly charged. However, they have the disadvantage that they produce a large amount of ozone.
Furthermore, the latter, i.e., charging apparatuses making use of contact with roller(s), have the advantage that they produce almost no ozone, charging of the photosensitive drum being accomplished as a result of causing the photosensitive drum surface to be contacted by roller(s) to which bias voltage(s) has or have been applied. However, as there is a tendency for roller surface(s) to deteriorate, it will be necessary to periodically carry out replacement of roller(s).
Art has therefore been disclosed, e.g. at Japanese Patent Application Publication Kokai No. 2000-235294 (hereinafter “Patent Reference No. 1”), in which an electrically conductive elastic roller is inserted within an electrically conductive tube, the electrically conductive tube and the electrically conductive elastic roller being made to rotate in idler fashion by the photosensitive body as the electrically conductive elastic roller is pressed against the photosensitive body. Because the inside diameter of the electrically conductive tube is greater than the outside diameter of the electrically conductive elastic roller, replacement thereof is simple, and it is possible to easily rejuvenate the electrically conductive tube surface when this has deteriorated due to contact with the photosensitive drum.
However, with Patent Reference No. 1, because there is a gap between the electrically conductive tube and the electrically conductive elastic roller, when the electrically conductive tube and the electrically conductive elastic roller are made to rotate in idler fashion by the photosensitive body, the locus at which the electrically conductive elastic roller contacts the electrically conductive tube is always changing in unstable fashion. This being the case, it is possible that resistance between the electrically conductive elastic roller and the photosensitive drum will be unstable, and that charging of the photosensitive drum by the electrically conductive elastic roller and the electrically conductive tube will also be unstable.
Accordingly, for stable charging of the photosensitive drum, there being no alternative but to employ a roller in which an electrically conductive film is in intimate contact with the roller surface, roller replacement has been unavoidable.
Furthermore, this sort of problem which has been described with respect to charging rollers has also been shared by charge removal rollers coming in contact with photosensitive drum(s) or the like and removing charge therefrom, cleaning rollers coming in contact with photosensitive drum(s) or the like and carrying out cleaning thereof, transfer rollers transferring development image(s) from photosensitive drum surface(s) to recording paper, and so forth, where it has also been necessary to carry out roller replacement in the event of deterioration of the roller surface.
The technology disclosed herein was therefore conceived in light of the foregoing conventional issues, it being an object thereof to provide a rotatable roller capable of imparting electric potential(s) in stable fashion and having outer circumferential surface(s) capable of being easily rejuvenated in the event of deterioration thereof.
Furthermore, it is an object of the technology disclosed herein to provide an image forming apparatus and an image forming apparatus cartridge employing the aforementioned rotatable roller(s) in accordance with the technology disclosed herein.